---
title: "JungJun Sung (@JungJun-Sung) | Hashnode"
description: "Full-Stack Developer | React, Next.js & Cloud Enthusiast (AWS/Docker). Read the latest articles by JungJun Sung on Hashnode."
url: "https://hashnode.com/@JungJun-Sung"
---

@JungJun-Sung

# JungJun Sung

@JungJun-Sung · Ottawa, ON, Canada · Joined January 2026

Full-Stack Developer | React, Next.js & Cloud Enthusiast (AWS/Docker)

### [MongoDB Schema Design: Lessons from Production](https://jungjun-sung.hashnode.dev/mongodb-schema-design-lessons-from-production?utm_source=hashnode&utm_medium=feed)

Embedding vs reference, denormalization, TTL indexes, Date comparison pitfalls - practical MongoDB schema design patterns from production.

6 min read · [jungjun-sung.hashnode.dev](https://jungjun-sung.hashnode.dev/mongodb-schema-design-lessons-from-production?utm_source=hashnode&utm_medium=feed)

[Feb 15](https://hashnode.com/posts/mongodb-schema-design-lessons-from-production/6991f3c5b88791e3dfb457c4)

### [React Native Performance Optimization: Patterns I Actually Applied](https://jungjun-sung.hashnode.dev/react-native-performance-optimization?utm_source=hashnode&utm_medium=feed)

FlatList tuning, image caching, React.memo, useNativeDriver - performance optimization patterns I applied in a real React Native app.

5 min read · [jungjun-sung.hashnode.dev](https://jungjun-sung.hashnode.dev/react-native-performance-optimization?utm_source=hashnode&utm_medium=feed)

[Feb 9](https://hashnode.com/posts/react-native-performance-optimization/698a33f8b6f5c77fb8b8816e)

### [Payment System with RevenueCat](https://jungjun-sung.hashnode.dev/payment-system-with-revenuecat?utm_source=hashnode&utm_medium=feed)

Dual verification pattern, server-side Entitlement verification, ownership transfer handling

7 min read · [jungjun-sung.hashnode.dev](https://jungjun-sung.hashnode.dev/payment-system-with-revenuecat?utm_source=hashnode&utm_medium=feed)

[Feb 7](https://hashnode.com/posts/payment-system-with-revenuecat/6987d18d9506921c684461e1)

### [How Clerk Saved Me Two Weeks](https://jungjun-sung.hashnode.dev/clerk-auth-webhook-design-en?utm_source=hashnode&utm_medium=feed)

Why Clerk for MVP, Svix raw body gotcha, idempotent user.deleted handling, and Auth Guard pattern in React Native

9 min read · [jungjun-sung.hashnode.dev](https://jungjun-sung.hashnode.dev/clerk-auth-webhook-design-en?utm_source=hashnode&utm_medium=feed)

[Feb 6](https://hashnode.com/posts/clerk-auth-webhook-design-en/698604ab63b3ddc52573911a)

### [What I Learned Separating Server State from Client State](https://jungjun-sung.hashnode.dev/what-i-learned-separating-server-state-from-client-state?utm_source=hashnode&utm_medium=feed)

Real patterns from using TanStack Query and Zustand together in a React Native app.

13 min read · [jungjun-sung.hashnode.dev](https://jungjun-sung.hashnode.dev/what-i-learned-separating-server-state-from-client-state?utm_source=hashnode&utm_medium=feed)

[Feb 5](https://hashnode.com/posts/what-i-learned-separating-server-state-from-client-state/6984fb2f8f138acaa7146868)